The present invention relates to water quality monitoring and control systems for use in devices wherein the phase of the water changes, such as ice makers, steamers, freezers, and/or humidifiers, and specifically relates to a system for operating such devices to maximize efficiency in the use of water and power.
Conventional devices which cause phase changes in water, including but not limited to ice makers, freezers, steamers and/or humidifiers, typically suffer from water-caused maintenance problems. For example, approximately 60% of maintenance costs on commercial ice making equipment are caused by water. Perhaps the greatest cause of equipment failure in ice making and steaming equipment is water-borne dissolved minerals commonly referred to as Total Dissolved Solids (TDS), measured in parts per million (ppm). Unacceptably large concentrations of TDS interfere with machine operation while in solution, and form deposits of unwanted scale when the water changes phase.
While in solution, excessive TDS concentrations can prevent the formation of ice cubes and produce undesirable cloudy appearing ice cubes. Scale deposits cause clogging of water lines, put additional loading on the pump, and act as an insulator which prevents the extraction of heat from the water. Harvesting of ice cubes becomes difficult in severely scaled ice makers as the formed cubes often become stuck to the evaporator plate, and eventually may damage the evaporator plate.
Further, in some cases, as TDS builds up in an ice maker, the pH of the water also increases, which decreases the ability of minerals to stay in solution. Thus, left unchecked, the scale forms progressively faster.
Conventional ice makers address the problem of TDS buildup by periodically flushing the water lines and other components during the harvest phase of the cube formation cycle. In addition, the storage sump, which retains a supply of chilled water recirculated to form ice cubes, is also emptied at this time, either partially or totally. Although effective in controlling TDS levels, these conventional procedures are extremely wasteful.
Specifically, water at ambient temperature must be purchased and directed to the sump, often filtered just prior to reaching the device, and power is expended to chill it to approximately 32.degree. F. Aside from the expense in obtaining the filtered, chilled water, in many areas there is also a sewer tax or other disposal expense which the commercial water user must pay to dispose of the flushed sump water. Considering that typical commercial ice makers operate continually on a cycle time of 18-25 minutes per cycle, and taking into account that large restaurant chains have multiple facilities each with at least one ice making machine, the total expenditure in water and power to remove excess TDS is quite significant. For example it has been estimated that a conventional ice making machine, operating continually, consumes approximately $2,800 worth of electricity and $300 worth of water on an annual basis.
In addition to the power and water costs, the service costs for removing scale from such equipment are significant. The de-liming or acid cleaning used to remove scale has also been found to deteriorate the corrosion-resistant coating, and otherwise shortens the working life of pumps and other expensive components.
Although the above discussion relates primarily to ice makers, similar problems occur with commercial steamers, wherein a supply of stored water is heated to form steam. On steamers, the scale forms on the heating surfaces as the water vaporizes, decreasing thermal efficiency and requiring more power to obtain required temperature levels. Also, related problems occur with humidifiers and commercial shaved ice makers.
Other attempts to decrease TDS and scaling in the water supply of ice makers, steamers and other water phase changing devices include the use of more effective filters and the addition of feed phosphates or acidulents to stop the buildup of minerals. Although filtration is effective in substantially reducing suspended particles, the ionic particles in solution in the water are not significantly reduced. One benefit of filtration is that it will prolong the service interval of ice making machinery. The addition of phosphates or acid to filtered water has also been found to further prolong the service interval as compared to filtration alone. The chemical additives assist in maintaining the ionic particles in solution longer. However, users of such equipment have still been forced to dump excessive amounts of chilled water from their units.
It has been known in the case of commercial steamers, which use significantly less water than do ice makers, to electronically and remotely monitor TDS content of treated water, and to provide a warning signal when TDS concentration exceeds preset limits. The warning signal indicates to the operator that the replaceable demineralizing cartridge must be changed. Such present systems, however, do not have sufficient capacity to operate and reduce the amount of chilled water which is periodically dumped from commercial ice making equipment, or of coordinating the consumption of water with the TDS concentration.
Another drawback of conventional water phase changing equipment is that the rate of scale buildup varies with the varying TDS concentration in different types of water sources, the level of water treatment, and the geographic region. It is also known that pH of water influences the TDS scaling effect of various concentration levels. However, conventional water phase changing equipment is incapable of coordinating control of pH with control of TDS and scaling.
Accordingly, it is an object of the present invention to provide an improved system for monitoring and controlling water quality in a water phase changing device to minimize the undesirable effect of TDS levels, and maximizing the efficiency of the use of water and power.
It is another object of the present invention to provide an improved system for monitoring and controlling a water phase changing device in which treated water is expelled and/or fresh water is introduced on an as needed basis as a function of a monitored TDS concentration to maintain the TDS concentration within preset limits.
It is yet another object of the present invention to provide an improved system for monitoring and controlling water quality whereby water-caused service intervals are substantially extended over conventional systems.
Still another object of the present invention is to provide an improved system for monitoring and controlling water quality in a water phase changing device wherein the pH is monitored and controlled to suit the water conditions of a particular installation.